Study On The Treatment Of Phenolic Coal Chemical Wastewater By Microbial Fuel Cell

The wastewater produced by coal chemical industry contains organic pollutants such as phenols and polycyclic aromatic compounds,which is a typical industrial wastewater that is difficult to degrade.In this study,Phenolic Coal Chemical Wastewater(PCCW)was treated in an anaerobic fluidized bed microbial fuel cell(AFB-MFC)filled with macroporous adsorptive resin(MAR)particles as multifunctional biocarrier.By the combination of simulation and experiment,the adsorption and diffusion mechanism of organic compounds in resin was studied.The degradation mechanism of organic compounds was revealed by energy analysis.In addition,response surface statistical method was used to optimize the process parameters and improve the performance of electricity generation and wastewater treatment capacity.The main research contents of the paper is as follows:Firstly,graphene(GR)modified cathode(PANI+Pt/C+GR)was prepared.Using polyaniline(PANI)as binder,GR was used to modify the cathode of carbon cloth(CC),and carbon nanotubes(CNTs)were used as control group.The modified electrodes were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),cyclic voltammetry(CV)and thermogravimetric analysis(TGA).These different cathodes were used in AFB-MFC to treat the PCCW.The results showed that the AFB-MFC output voltage and COD removal rate of PANI+Pt/C+GR were the highest,reaching 512.20 mV and 84.37%,respectively.Secondly,MAR was selected as a multifunctional biological carrier in AFB-MFC,and the mechanism of MAR in the device was revealed.The specific surface area and pore structure of MAR and granular active carbon(AC)were analyzed by BET test method.And AFB-MFC wastewater treatment and electricity generation performance were investigated.MAR,which is widely used in wastewater treatment,was selected as fluidized particle in AFB-MFC.In addition,SEM was used to observe the adhesion of a large amount of spherical biomass on the surface of MAR,indicating that microorganisms successfully loaded onto MAR.Sorption heat relationship between organic compounds in PCCW and MAR was established by the Sorption module of Materials Studio(MS)software.The average adsorption heat of MAR for m-cresol,phenol and benzene was 65.4961,57.1164 and 47.7362 kJ/mol,respectively.Molecular dynamics simulation was used to study the diffusion of organic molecules in MAR.The diffusion coefficient of MAR for m-cresol,phenol and benzene was0.04350,0.03088 and 0.02297(?)~2/ps.The simulation results showed that MAR had the strongest adsorption effect on m-cresol,followed by phenol,and the weakest on benzene.Furthermore,the adsorption and diffusion mechanism obtained by molecular simulation was verified by the pseudo-second-order model.Thirdly,AFB-MFC process parameters were optimized by response surface statistical method.The initial COD concentration,flow rate and external resistance were the major influencing factors,and the COD removal rate and the maximum power density were the response values.The Box-Behnken design-Response Surface Method(BBD-RSM)in Design-Expert 8.0.6 statistical software was used to design 17groups of three-factor and two-level experiments.The quadratic polynomial regression equation,response surface and contour plot of the two response values about the three factors were obtained.The optimum process conditions of AFB-MFC were determined as follows:COD initial concentration of 1815.23 mg/L,flow rate of 57.66 mL/min,and external resistance of 5187.77Ω.Under this process condition,the COD removal rate and the maximum power density could reach 93.314%and 139.013 mW/m~2,respectively.Fourthly,by the combination of simulation and experiment,the degradation mechanism of PCCW in AFB-MFC was revealed.High-throughput sequencing results of microorganisms in AFB-MFC activated sludge showed that at the phylum level,Proteobacteria,Firmicutes and Chloroflexi bacteria adapted to the MFC environment and became the dominant bacteria.At the genera level,Acinetobacter,Aeromonas,Pseudomonas and Sulfurospirillum were screened out and became the dominant bacteria.Based on the electron cloud density analysis of m-cresol,phenol,benzene and their intermediate products,the degradation pathway of organic compounds was predicted.The degradation intermediates of m-cresol were determined by headspace gas chromatography mass spectrometry(HS-GC-MS)as 4-methyl-2-pentanone and acetic acid,and the degradation intermediates of phenol were cyclohexanone,hydroxyhexanedither and hydroxyacetic acid.The degradation of m-cresol and phenol with 4-methyl-2-pentanone and cyclohexanone as intermediates was verified.In addition,TS-Search and TS-Confirmation functions of MS software were used to analyze the energy of degradation pathway.The results showed that the controlling step of m-cresol degradation pathway was the first step,and the energy barrier needed to break through was 94.9920 kcal/mol.The degradation control steps of phenol and benzene were the third and first steps,and the energy barriers to be broken were134.5880 kcal/mol and 190.0170 kcal/mol,respectively.